His cluelessness is actually what does make Trump terrifying more then anything else:
"'You do know you just attacked a Gold Star family?' one adviser warned Trump
Trump didn’t know what a Gold Star family was: 'What’s that?' he asked."
"Believe me, she would not be my first choice, that I can tell you." –Donald Trump, mocking the women who alleged he sexually assaulted them, suggesting his accusers weren't attractive enough to earn his attention.
"You know I’m automatically attracted to beautiful — I just start kissing them. It’s like a magnet. Just kiss. I don’t even wait. And when you’re a star, they let you do it. You can do anything. Grab them by the p**sy. You can do anything."
“I don’t think anybody knows it was Russia that broke into the DNC. [Clinton’s] saying Russia, Russia, Russia, but I don’t — maybe it was. I mean, it could be Russia, but it could also be China. It could also be lots of other people. It also could be somebody sitting on their bed that weighs 400 pounds, OK?”
"40 Wall Street actually was the second-tallest building in downtown Manhattan... And now it’s the tallest." –Donald Trump, bragging about his building following the 9/11 attack on the World Trade Center
“When Iran, when they circle our beautiful destroyers with their little boats, and they make gestures at our people that they shouldn’t be allowed to make, they will be shot out of the water." –Donald Trump, threatening to go to war with Iran over rude hand gestures
"Dwyane Wade's cousin was just shot and killed walking her baby in Chicago. Just what I have been saying. African-Americans will VOTE TRUMP!" –Donald Trump, tweeting about the tragic death of Nykea Aldridge, cousin of NBA star Dwyane Wade, and making it all about him
"What do you have to lose by trying something new like Trump?
What do you have to lose? You’re living in poverty; your schools are no good; you have no jobs; 58 percent of your youth is unemployed. What the hell do you have to lose?" –Donald Trump, making a pitch to win over African American voters, adding, "At the end of four years, I guarantee you that I will get 95 percent of the African-American vote."
"Why can’t we use nuclear weapons?" –Donald Trump, reportedly asking a foreign policy adviser three times during a meeting why the U.S. couldn’t use its nuclear weapons stockpile
Essentially he seems to think bullying and intimidation is the key to making America safe, and alienating allies whilst sucking up to strongmen is the way to make America great.